feat: add TripAdvisor username scan module

[brunolm]

Adds a username-existence scan module for TripAdvisor.

How it works

• GET https://www.tripadvisor.com/Profile/{username} via generic_validate (mirrors zomato.py).
• Found → HTTP 200, or a 301/302 that redirects back to /Profile/... (TripAdvisor case-canonicalizes handles, e.g. travelbug → /Profile/TRAVELBUG, so a redirect to a profile URL still confirms the account exists).
• Not found → HTTP 404.
• No Cloudflare wall; reachable over plain httpx.

Testing

• Verified live: real handles (including a real account) return Found, well-formed nonexistent handles return Not Found.
• Auto-discovered (no registry changes). Full test suite passes (only the pre-existing *_unreadable tests fail, and only on Windows).

Context

This fills a real coverage gap: Maigret and WhatsMyName check TripAdvisor usernames but user-scanner did not. (Other apparent gaps like Strava/Yelp/Slack usernames turned out to be numeric-ID or workspace-slug checks, not real user lookups.)

[brunolm]

DataDome